Magnetic thin film wire with multiple laminated film coating



J1me 1969 AKIRA MATSUSHITA 3,451,793

MAGNETIC THIN FILM WIRE WITH MULTIPLE LAMINATED FILM COATING Filed Dec. 12, 1966 FIG. 4

Ni I

COERCIVE FORCE. HC 0 m 4 m TEMPERATURE INVENTOR.

' mum nm-susni-m Patented June 24, 1969 rm. Cl. Hillb 1/02 US. Cl. 29194 7 Claims This invention relates to wires coated with magnetic thin films (herein referred to as magnetic thin film wire) suitable foruse principally in memory elements and parametron elements. More particularly the invention concerns a new and improved magnetic thin film wire which is not subject to magnetostriction, has almost zero temperature coeflicient, and has extremely stable characteristics.

Magnetic thin film wires of the type referred to above consist of a conductor core wire coated with a magnetic thin film such as Permalloy applied on the conductor wire by electrodeposition. In general, since the magnetic thin film is affected by ambient temperatures, variations in temperature cause fluctuations in the magnetic characteristics, particularly the coercive force He, and, moreover, is readily subjected to magnetostriction.

It is an object of the present invention to provide a magnetic thin film wire which is almost completely free of magnetostriction, having a temperature coefficient close to zero, and having a remarkably stable characteristics.

Briefly stated, a feature of the magnetic thin film wire of the invention is that on the surfaces of a single conductor core wire, at least one thin film of an iron-nickel alloy of a compositional ratio of 50 percent of iron and 50 percent of nickel and at least one thin film of an iron-' nickel alloy of a compositional ratio of 21 percent of iron and 79 percent of nickel are deposited in laminate arrangement.

The nature and details of the invention will be more clearly apparent from the following detailed description with respect to preferred embodiments of the invention when read in conjunction with the accompanying drawing, in which like parts are designated by like reference numerals.

In the drawing:

FIGS. 1, 2, and 3 are fragmentary perspective views, with parts cut away, showing examples of magnetic thin film wire embodying the invention; and

FIG. 4 is a graphical representation indicating the relationship between temperature and coercive force in various components of the magnetic thin film wire according to the invention.

Referring to FIGS. 1, 2, and 3, there are shown examples of magnetic thin film wire embodying the invention. In each wire, a conductor core wire 1 is coated with at least one magnetic thin film 2 of an allow (hereinafter referred to as allow A) of 50 percent Fe and 50 percent Ni, and at least one magnetic thin film 3 of an alloy (hereinafter referred to as alloy B) of 21 percent Fe and 79 percent Ni.

FIG. 1 illustrates the most simple example in which the conductor core wire 1 is coated with one film 2 of alloy A which in turn is coated with one film 3 of alloy B. According to the invention, a plurality of alternate layers of films 2 and 3 may be deposited as illustrated in FIG. 2. I

Furthermore, an intermediate layer 4 of a conductor such as gold, silver, and copper or an insulating material can be interposed between magnetic thin films 2 and 3 as illustrated in FIG. 3. In this case, mutual interference between the magnetic thin films 2 and 3 can be reduced, and, by suitably selecting the material, thickness, and other features. of the intermediate film layer 4, magnetic thin film wires of various magnetization characteristics can be obtained.

The magnetization easy axes of the magnetic thin films 2 and 3 can be respectively selected as desired to be in the wire circumferential direction or the wire axial direction, it being possible to cause the two easy axes to be in the same direction or to be independently in different directions.

Alloy A (50% Fe, 50% Ni) and alloy B (21% Fe, 79% Ni) both have compositions which are not subject to magnetostriction and their respective temperature characteristics are as indicated in FIG. 4.

I have found that when a magnetic thin film wire is provided with composite layers of films of alloys A and B according to the invention, the temperature characteristic of the entire magnetic thin film wire becomes that as indicated by curve C in FIG. 4, whereby the temperature coefficient with respect to He is almost zero.

Moreover, since both of the alloys A and B have composition which, from the beginning, are not subject to magnetostriction, it is possible to produce a magnetic thin film wire which is not subject to magnetostriction, has practically zero temperature coefficient, and has extremely stable characteristics even when films of the alloys A and B are deposited in composite arrangement.

It should be understood, of course, that the foregoing disclosure relates to only preferred embodiments of the invention and that it is intended to cover all changes and modifications of the examples of the invention herein chosen for the purposes of the disclosure, which do not constitute departures from the spirit and scope of the invention as set forth in the appended claims.

What I claim is:

1. A magnetic thin film wire comprising a conductor core wire, at least one first film of an iron-nickel alloy containing 50 percent of iron and 50 percent of nickel, and at least one second film of an iron-nickel alloy containing 21 percent of iron and 79 percent of nickel, said first and second films being deposited to envelope the conductor core wire in alternate laminated layers.

2. A magnetic thin film' wire comprising a conductor core wire, at least one first film of an iron-nickel alloy containing 50 percent of iron and 50 percent of nickel, at least one second film of an iron-nickel alloy containing 21 percent of iron and 79 percent of nickel, and at least one intermediate film, said first and second films being deposited to envelope the conductor core wire in alternate laminated layers with said intermediate film interposed between adjacent first and second film.

3. The magnetic thin film wire as claimed in claim 2 in which the intermediate film is an electrical conductor.

4. The magnetic thin film as claimed in claim 2 in which the intermediate film is an electrical insulator.

5. The magnetic thin film wire as claimed in claim 1 in which all first and second films are caused to have magnetization easy axes in the wire axial direction.

6. The magnetic thin film wire as claimed in claim 1 in which all first and second films are caused to have magnetization easy axes in the wire circumferential direction.

7. The magnetic thin film wire as claimed in clainrl ""3-,-2-13,43'1 10/ 1965 Kolk etal. '340-174 in which either of the first and second films is caused to 3,328,195 6/1967 May 29-194 X have a. magnetization easy axis in a first direction and 3,350,180 10/1967 Croll 29--183.5 the other is caused to have a magnetization easy axis in a 3,375,091 3/1968 Feldtkeller 29--194 direction different from said first direction. 5

L. DEWAYNE RUTLEDGE, Primary Examiner.

References Cited E. L. WEISE, Assistant Examiner.

UNITED STATES PATENTS 2,853,402 9/1958 BlOiS 340-174 X 3,089,228 5/1963 Lynch 29-194 10 29 19s, 196.1, 196.6; 340 174 

1. A MAGNETIC THIN FILM WIRE COMPRISING A CONDUCTOR CORE WIRE, AT LEAST ONE FIRST FILM OF AN IRON-NICKEL ALLOY CONTAINING 50 PERCENT OF IRON AND 50 PERCENT OF NICKEL, AND AT LEAST ONE SECOND FILM OF AN IRON-NICKEL ALLOY CONTAINING 21 PERCENT OF IRON AND 79 PERCENT OF NICKEL, SAID FIRST AND SECOND FILMS BEING DEPOSITED TO ENVELOPE THE CONDUCTOR CORE WIRE IN ALTERNATE LAMINATED LAYERS. 